Pope John Paul II has said man's "ecological vocation" is more urgent than ever, given the grave threats to the environment.

The Holy Father delivered his message on Sunday on the eve of the UN World Summit on Sustainable Development, which opened yesterday in Johannesburg, South Africa.

"The human creature feels very little before the wonder of divine Providence, manifested in creation and history," John Paul II said, before reciting the Angelus with several thousand pilgrims gathered at the Castelgandolfo papal summer residence south of Rome.

"At the same time, [the human creature] realises that he is the recipient of a message of love that calls him to responsibility," the Holy Father said. "People, indeed, are appointed by God as administrators of the earth, to cultivate and protect it."

"From here stems that which we might call their 'ecological vocation,' which in our time has become more urgent than ever," he said.

Referring to the Johannesburg summit, the Pope said: "We all hope that the numerous heads of state and government present, and the other participants, will succeed in finding effective ways for an integral human development, keeping in mind the economic, social and environmental dimension."

"In a world that is increasingly interdependent, peace, justice and the protection of creation must be the fruit of the common effort of all in pursuing the common good together," the Holy Father added.